Photopolymerizable pigmented vehicles containing chlorosulfonated or alpha-haloalkylated benzanthrone initiators

ABSTRACT

PHOTOPOLYMERIZATION OF ETHYLENEICALLY UNSATURATED ORGANIC COMPOUNDS UTILIZING PHOTOSENSITIVE CATALYSTS OF THE HALOGENATED POLYNUCLEAR KETONE TYPE IS DISCLOSED. RAPID POLYMERIZATION OR CURE IS OBSERVED EVEN IN THE PRESENCE OF ORGANIC AND INORGANIC PIGMENTS.

United States Patent O "ice PHOTOPOLYMERIZABLE PIGMENTED VEHI- CLES CONTAINING CHLOROSULFONATED OR a-HALOALKYLATED BENZANTHRONE INITIATORS Vincent Daniel McGinniss, Middleburgh Heights, Ohio,

assignor to SCM Corporation, Cleveland, Ohio No Drawing. Filed Jan. 12, 1973, Ser. No. 323,087

Int. Cl. C08d 1/00; C08f 1/16 US. Cl. 204--159.23 9 Claims ABSTRACT OF THE DISCLOSURE Photopolymerization of ethylenically unsaturated organic compounds utilizing photosensitive catalysts of the halogenated polynuclear ketone type is disclosed. Rapid polymerization or cure is observed even in the presence of organic and inorganic pigments.

BACKGROUND OF THE INVENTION The present invention is concerned with photopolymerizable compositions and a process for producing the same by exposure to ultraviolet radiation in the presence of a photosensitive catalyst.

DESCRIPTION OF THE PRIOR ART It is known that the photopolymerization of ethylenically unsaturated monomers can be initiated by exposure to various sources of radiation such as ultraviolet radiation. For example, methyl acrylate on long standing in sunlight will generally transform into a transparent mass. Use of sunlight or sources of comparable energy to photopolymerize monomers or combination of monomers,-

oligmers, etc is not practical because of very slow rates of polymerization. Improved rates can be induced by thermal energy, however, particularly in combination with free-radical promoting catalysts. Thermal energy or heat for this purpose has been supplied by conventional convection ovens and radiant heat from infrared sources to effect the desired rate of polymerization. However, for many applications and especially in the coating art, heat for curing purposes is no longer satisfactory because (I) it is still slow; (2) it cannot be used with heat-sensitive substrates; and (3) often use of a volatile solvent is necessary, which solvent becomes a potential air pollutant or costly to recycle.

T o enhance the rate of polymerization of ethylenically unsaturated organic compounds by exposure to radiation such as ultraviolet radiation photoinitiators or photosensitizers are included with said organic compounds. Typical photosensitizers have been benzene sulfonyl chloride, p-toluene sulfonyl chloride, naphthalene sulfonyl chloride, zinc and cadmium sulfides, and sulfinic and phosphinic compounds. These prior art photoinitiators, however, have not been completely satisfactory, particularly in photopolymerizable compositions which contain pigments. For clarity, the term photopolymerization composition refers to that composition which hardens (cures) upon exposure to radiation and which can be a vehicle or a binder for use in surface coatings such as paint, varnish, enamel, lacquer, stain or ink.

Typical sources for ultraviolet radiation include a number of commercial units such as electric arc lamps, plasma arc torch (see U.S.P. No. 3,364,387) and even laser having a lasing output in the ultraviolet spectrum (see copending application of deSouza and Buhoveckey, Ser. No. 189,254). The subject matter of the aforementioned patent and patent application are incorporated herein by 3,827,956 Patented Aug. 6, 1974 of UV. energy, particularly that in wave lengths between about 3200 A. and 4000 A. to perform cold polymerization (curing) of the vehicle at very short exposure times with attendant suppression of losses due to volatilization of components of paint, suppression of discoloration or degradation of the resulting deposit (which can be generally considered a film) and avoidance of shrinkage and distortion (the preservation of dimensional stability) and suppression of degradation of the-substrate is a plastic, or paper, or fabric.

SUMMARY OF THE INVENTION In accordance with the present invention, there is provided a process for the photopolymerization of ethylenically unsaturated organic compounds, which comprises subjecting to a source of ultraviolet radiation having wave lengths from about 1800 to 4000 Angstroms a composition comprising a photopolymerizable ethylenically unsaturated compound, a pigment and a photoinitiator selected from halogenated polynuclear ketones. The pigment which can be organic or inorganic can be present up to about 50% by weight of the composition, whereas the halogenated polynuclear ketone should be present in amounts of about 0.5 to 19% by weight.

Examples of such halogenated polynuclear ketones are: Chloromethylbenzanthrone, benzanthrone sulfonyl chloride, on bromoethylbenzanthrone, 1,6 dichlorosulfonyl benzanthrone, isodibenzanthrone sulfonyl chloride and dichlorosulfonyl-l6,l7-dibenzanthrone. The basic ketones are commercially available and their halogenated versions can be prepared conveniently by. known methods such as chlorosulfonation, haloalkylation and halogenation techniques.

The needed proportion of instant halogenated polynuclear ketone sensitizer can be incorporated directly into the vehicle as a unit of a further polymerizable monomer, oligomer, prepolymer, or polymer vehicle. In such instance, for example, the sensitizer compound has a reactable functional group on it such as carboxyl group or a hydroxyl group. Thus each sensitizer compound can be made to react with a further polymerizable material, e.g., glycidyl acrylate, either in monomeric form or already part of a preformed prepolymer or oligomer.

Typically the vehicles can constitute the entire deposit or a binder for solids to yield a cured product in the nature of a paint, varnish, enamel, lacquer, stain or ink. Usually the vehicles are fluid at ordinary temperature operation (between about 30 F. and about 300 F. and advantageously between ordinary room temperature and about 180 F.), and when polymerized by the UV. radiation, give a tack-free film or deposit that is durable enough for ordinary handling. In the cured state such vehicle is resinous or polymeric in nature, usually crosslinked. Uncured for application to a substrate or uncured on such substrate, such vehicle consists essentially of a monomer or mixture of monomers, or a further polymerizable oligomer, prepolymer, resin, or mixture of same, or a resinous material dispersed or dissolved in a solvent that is copolymerizable therewith. Such solvent ordinarily is monomeric, but can be an oligomer (i.e., up to 4 monomer units connected) or prepolymer (mol weight rarely above about 2000). Oligomers and prepolymers should be understood herein as being polymeric in nature.

Suitable ethylenically unsaturated compounds which are photopolymerizable with the aid of the above photoinitiators include the various vehicles or binders which can be reactive vinyl monomers such as the lower alkyl esters of acrylic and methacrylic acids or polymer and prepolymers. Vinyl monomers particularly adapted for photopolymerization include methylmethacrylate, ethylmethacrylate, 2-ethylhexyl methacrylate, butylacrylate, isobutyl methacrylate, the corresponding hydroxy acrylates; e.g., hydroxy ethylacrylate, hydroxyl propyl acrylate, hydroxy ethylhexyl acrylate, also the glycol acrylates; e.g., ethylene glycol dimethacrylate, hexamethylene glycol dimethacrylate, the allyl acrylates; e.g., allyl methacrylate, diallyl methacrylate, the epoxy acrylates; e.g. glycidyl portions. These resins were acrylic monomers, diacrylate and triacrylate oligomers.

A polymerizable composition consisting of A Z-ethylhexyl acrylate, /3 ethylene glycol diacrylate, and /3 trimethylolpropane triacrylate was prepared with various methacrylate; and the aminoplast acrylates; e.g., melamine 5 photo-initiators in accordance with the present invention. acrylate. Others such as vinyl acetate, vinyl and vinyl- To each composition was added conventional pigment idene halides and amides, e.g., methacrylamide, acryland at various pigment-to-binder ratios ranging from .2 amide, diacetone acrylamide, butadiene, styrene, vinyl to .9 parts pigment per 1 part binder. The pigment was toluene, and so forth are also included. dispersed within the binder in a conventional manner.

Not only is the speed of U.V. curing quite good using Each sensitized binder composition was poured over a the present sensitizers, but also the depth of cure is quite pair of steel panels and drawn down with a No. 8 wound practical so that the resultant polymerized deposit resists wire rod to a film thickness or coating of approximately scratching or disruption when first ostensibly dry on 0.5 ml. The coated but wet panels were each exposed the surface. Curing can continue on stored pieces. Typical to a different source of ultraviolet light; one provided from film thickness for the deposit can be about 0.1 to as high a plasma arc radiation source (PARS) and the other a as 10 mils. Preferred cured deposits are continuous films, conventional ultraviolet light supplied by Ash Dee Corpobut decorative or message-transmitting ones need not be. ration, said light having two 4,000 watt mercury lamps. Typically the substrate workpieces coated with the un- Exposure times were from 0.07 sec. to 30 secs., with the cured deposit or deposits are passed under a U.V.-provid- 2O panels being placed approximately 5 inches from the ultraing light beam by a conveyor moving at predetermined violet source. These exposure times are calculated from speeds. The substrate being coated can be metal, mineral the speed of the conveyor belt on which the panels are glass, wood, paper, plastic, fabric, ceramic, etc. placed. For example, a speed rate of 300 feet per minute A distinct advantage of the present invention is that corresponds to 0.07 second exposure time, whereas the many useful pigments can be incorporated, in modest speed of approximately 86 to 100 feet per minute corproportions, into the vehicle without much deleterious responds to 0.2 seconds. The photopolymerization was effects. Thus, opacifying pigments such as zinc oxide can done in an inert atmosphere as described earlier. be used quite well. Titania, e.g., anatase and particularly In Table I below there are shown the results of exposrutile, can also be used with case even though it makes ing panels coated with various combinations of pigment for a much more difficult film to cure by U.V. radiation. to binder ratios and which also included prior art photo- Other filler materials and coloring pigments such as basic initiators and those of the present invention. Under the lead sulfate, magnesium silicate, silica, clays, wollastonite, column designated cure, the nature of the finished or talcs, mica, chromates, iron pigments, wood flour, microcured films is described. For example, tacky indicates that balloons, hard polymer particles, and even reinforcing the film is still soft to the touch; i.e., incomplete polymglass fiber or flake also are suitable in the vehicle to make erization. The term, hard, on the other hand indicates a paint. Generally little to no pigments are used in photofull cure.

TABLE I Pigment and pigment-to- Time Photoinitator, percent wt. binder ratio U.V. source sec Cure l-chloromethyi naphthalene, 2% Rutile T102 (0.5)- PARS 0. 2 Tacky and Do-- .do..- Conventional-.. 7 glu Ohloromethylbenzanthrone, 2% go PARS 0.2 Hard. makk iioi (0.5 PARS 0.; 331 Copper phthalocy PARS 0.2 Do.

8.111118 greens. Benzanthrone sulfonyl chloride, 2% Rutiie 'IiO; (0.7).--. PARS 0. 2 Do.

Do- Rutile IiOz (0.9).--. PARS 0.2 Do.

Do- Antase Tl02 (0.8)--. PARS 0.2 Do. 2-bromomethylbenzauthrone, 2%--- 0.2 Do. 1,G-diehlorosulfonylbenzanthrone, 2%- 0.2 Do. Isodibenzanthrone sulfonyl chloride, 2 O. 2 Do.

polymerizable vehicles because of the attendant difliculty of rapid curing. Pigment particles tend to absorb the bulk of the useful ultraviolet radiation and leaving only a minor portion of said radiation to energize the sensitizers and generate the requisite amount of necessary free radicals.

The following examples show ways in which this invention has been practiced, but should not be construed as limiting it. Unless otherwise specifically stated herein, all parts are parts by weight, all percentages are weight percentages, and all temperatures are in degrees Fahrenheit. Where the binder being cured is of the type normally curable by free-radical polymerization, it is sometimes advantageous for completeness of .cure and speed to maintain a substantially inert atmosphere above the irradiated workpiece. Generally this is effected by maintaining a purge of nitrogen or other inert gas or placing a thin film of completely transparent polyethylene over the workpiece.

EXAMPLE 1 A number of acrylic resins and combinations thereof were utilized in evaluating the photoinitiator of the present invention. For convenience, the polymerizable binder composition comprised three acrylic resins in equal pro- EXAMPLE 2 A clear vehicle is prepared first from /3 part pentaerythritol triacrylate, /3 part hydroxyethyl acrylate, and V3 the adduct formed by reacting one mol of toluenediisocyanate with 2 mols of hydroxyethyl acrylate. Anatase TiO is incorporated into said clear vehicle to provide a pigment to vehicle (binder) ratio of 0.6.

The curing procedure is carried out in the same manner described in Example 1. Without the incorporation of any sensitizers no curing (hardening) of the coated film (0.5 mil) is observed even with repeated exposures to the U.V. source. (Panels coated with the pigmented vehicle to about 0.5 mil thickness are passed under the PARS U.V. radiation source at line speeds of feet per minute for 100 consecutive times without any observable curing).

Chloromethylbenzanthrone is incorporated into the pigmented vehicle to the extent of 2% and the panels coated with the sensitized vehicle are irradiated by the PARS ultraviolet source described in Example 1 at line speeds of 100 feet per minute showing full cure. With conventional ultraviolet the time was 7 seconds.

Other pigments are incorporated such as zinc oxide, iron black, copper phthalocyanine blues and greens all resulting in the same hard cure after comparable exposure times.

EXAMPLE 3 A clear vehicle is prepared from /2 tri-methylolpropane and /2 2-ethylacrylate. Into said vehicle is incorporated separately (with pigment to vehicle ratio of 0.5) a series of pigments, i.e., rutile THiOg, anatase, TiO iron black, antimony oxide, lead basic sulfate, copper phthalo cyanine greens. Into each sample is incorporated 2% by weight of p-toluene sulfonyl chloride. The samples are reduced to films (0.4 mil) on aluminum panels and irradiated with the PARS U.V. source at line speed of 100 feet per minute. No observable cure is shown even after repeated exposures. Into identical portions of the pigmented vehicles is incorporated 2% by weight of abromoethylbenzanthrone. Full cure is shown after one exposure (0.2 sec.). The efiectiveness of the photoinitiator is comparable for all the pigmented vehicles.

EXAMPLE 4 Repeating the same procedure of Example 3 except benzanthrone sulfonyl chloride is utilized. The same eX- cellent results are obtained.

EXAMPLE 5 Repeating the same procedure of Example 3 except 1,6- dichlorosulfonylbenzanthrone is utilized as the photoinitiator. Again the same excellent results are obtained.

EXAMPLE 6 The pigmented and sensitized vehicles of Example 3 are applied in films 0.4 mil thick onto cardboard and paper substrates. The films were cured in the same manner described in Example 1. The cure is hard and no distortion or degradation of either substrate is observed.

What is claimed is:

1. A pigmented vehicle photopolymerizable on exposure to ultraviolet radiation, comprising an ethylenically unsaturated organic compound, a pigment and a photoinitiator selected from the group consisting of chlorosulfonated benzanthrones, ot-haloalkylated benzanthrones and mixtures thereof, said pigment comprising from about 20% to about by weight of said vehicle and said photoinitiator being in the range of 0.5 to 10% by Weight of said vehicle.

2. The pigmented vehicle of claim 1 wherein said photoinitiator is chloromethyl benzanthrone.

3. The pigmented vehicle of claim 1 wherein said photoinitiator is benzanthrone sulfonyl chloride.

4. The pigmented vehicle of claim 1 wherein said photoinitiator is 1,6-dichlorosulfonyl benzanthrone.

5. The pigmented vehicle of claim 1 wherein said photoinitiator is isodibenzanthrone sulfonyl chloride.

6. The pigmented vehicle of claim 1 wherein said photoinitiator is dichlorosulfonyl-l6,17-dibenzanthrone.

7. The pigmented vehicle of claim 1 wherein said pigment is an opacifying pigment.

8. The pigmented vehicle of claim 1 wherein said photoinitiator is 2% by weight, based on the weight of the vehicle.

9. The pigmented vehicle of claim 7 wherein the pigment is selected from organic and inorganic pigments.

References Cited UNITED STATES PATENTS 3,702,812 11/1972 McGinniss 204159.24 2,579,095 12/1951 Sachs et al 204159.24 3,113,024 12/1963 Sprague et a1. 9685 OTHER REFERENCES Suter: Organic Chemistry of Sulfur Compounds, J. Wiley & Sons, Chapter V.

MURRAY TILLMAN, Primary Examiner R. B. TURER, Assistant Examiner U.S. Cl. X.R.

96-115 P; 117-93.31, 124 R, 132 R, 138.8 R, 143 A; 204-159.14, 159.16, 159.18; 159.24; 260-2.5 B, 39 P, 39 M, 39 SB, 41 A, 41 B, 41 C, 41 AG, 77.50 R, 80.75, 80.81, 86.1 E, 851, 856 

